Simple use of windowManager

package com.softeem.android;

import android.app.Activity;
import android.app.Dialog;
import android.os.Bundle;
import android.view.Window;
import android.view.WindowManager;
import android.widget.Button;
import android.widget.LinearLayout.LayoutParams;

public class MainActivity extends Activity {
	/** Called when the activity is first created. */
	@Override
	public void onCreate(Bundle savedInstanceState) {
		super.onCreate (savedInstanceState);
		 setTheme(R.style.Transparent);    
		setContentView(R.layout.main);
		Button btn = new Button(getApplicationContext());
		btn.setText("Is this a floating window?");
		WindowManager wm = (WindowManager) getApplicationContext ()
				.getSystemService("window");
		WindowManager.LayoutParams wmparams = new WindowManager.LayoutParams ();

		wmparams.type = 2002;
		wmparams.format = 1;
//		wmparams.width = getWindowManager().getDefaultDisplay()
//				.getWidth();
//		wmparams.height = getWindowManager().getDefaultDisplay().getHeight();

		 // wmparams.flags = 100;
		 wmparams.width = 300;
		 wmparams.height = 300;
		wm.addView(btn, wmparams);
		
		Dialog dg =new Dialog(this);
		Window window = dg.getWindow();
		WindowManager.LayoutParams lp =window.getAttributes();
		lp.alpha =0.2f;
		window.setAttributes(lp);

	}
}

    <application android:icon="@drawable/icon" android:label="@string/app_name">
        <activity android:name=".MainActivity"
                  android:label="@string/app_name"
                  android:theme="@style/Transparent">  
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>

    </application>
    <uses-sdk android:minSdkVersion="10" />
<uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW" />